RENAL PARENCHYMAL MALACOPLAKIA - ULTRASTRUCTURAL FINDINGS IN DIFFERENT STAGES OF MORPHOGENESIS

Light microscopic and ultrastructural findings in five cases of renal parenchymal malakoplakia detected in renal biopsy specimens (four case s) or observed at autopsy (one case) are reported. The spectrum of ult rastructural changes ranging from lamellar and microvesicular phagolys osomal inclusions arranged in a biphasic pattern to fully developed Mi chaelis-Gutmann bodies is described. In three of the biopsy cases the lesions appeared to represent early stages of malakoplakia lacking cla ssic Michaelis-Gutmann bodies. Especially in this phase of disease, ul trastructural investigation can distinguish between this condition and other histiocytic interstitial renal processes. The findings show tha t focal cytoplasmic degeneration and autophagolysosomal processes obse rved in macrophages could precede the disturbance in the process of ba cterial breakdown that is responsible for the peculiar granuloma-like inflammatory histiocytic reaction.